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In today's highly competitive marketplace, businesses simply cannot tolerate downtime. In fact, market research...
firm IDC estimated that downtime costs Fortune 1000 firms between $100,000 and $1 million per hour, depending on the application. While VMware offered higher availability than traditional premises systems, its High Availability approach had some flaws. The vendor addressed certain limitations with the new vCenter Server 6.5, but a few potential issues remain.
Nowadays, improving uptime is a goal for businesses of all sizes.
"Many companies are trying to get their system availability up to five nines -- or higher," said Marco Alcala, CEO at Alcala Consulting Inc., which delivers IP services to medium and small organizations. Five nines -- 99.999% -- availability translates to systems being offline for about five minutes each year.
Initially, one reason why VMware became popular was because it enabled enterprises to run multiple VMs on a single device. The vendor's approach reduced costs, but had limitations as a High Availability (HA) offering. The single system becomes a potential central point of failure. If an issue, like a faulty line card, arises, then all of its applications may be knocked offline.
Taking the next steps in HA
Clustering takes virtualization concepts one step further. Here, a group of tightly connected computers work together so that, in many respects, they perform like a single system. Redundancy improves because there is more than one server in the cluster. If a hardware problem arises with one server, another one takes over.
VMware supports HA through vSphere servers and vCenter, its management console. Traditionally, the vendor relied on Microsoft Windows clustering functions to add redundancy, but vCenter Server 6.5 no longer has that design. Instead, businesses rely on multiple vSphere Servers for HA.
The new release also automates more failover functions, which should help companies improve uptime. Previously, the process of moving applications from problem systems to functioning servers took half an hour or more, depending on the system configuration. The new release is built to support five nines uptime, meaning failover should occur in about five minutes.
Also, previous versions offered businesses little granularity. The latest release of vCenter Server 6.5 provides customers with three options for invoking HA processes. A passive mode occurs whenever problems arise that knock a system offline. With active services, hardware vendors write scripts to inform vSphere of potential host issues.
The trigger sparks an HA action before the server begins going down; for instance, the system would make a switch if a chassis stared to overheat. The Witness feature combines both active and passive functions as hosts fail.
Gaining more options
In addition, vCenter Server 6.5 users gain more control over the failover process. If three servers -- database, application and web -- all support one application, the IT department can sequence the system restart, say booting the database server first, then the application system and finally the web server.
Finally, a new status mode, called Quarantine Mode, keeps troubled VMs from causing additional problems. These systems now run on a host only when absolutely necessary.
Alcala Consulting relies heavily on VMware to support its services and plans to upgrade to vCenter Server 6.5. "We think the new capabilities will enable us to improve system performance and operate more efficiently," Alcala stated.
Better, but not quite a panacea
Despite these advances, some limitations remain. HA features are expensive. Typically, the cost of such a system starts at $250,000 and can even surpass the $1 million mark.
Zero downtime, the lofty goal of many organizations, remains elusive. VCenter Server 6.5 has a Recovery Time Objective of about five minutes, but the actual recovery performance will vary depending on the server load, size and capabilities.
Finally, support for the new features has to be integrated into other tools associated with failovers. For instance, Alcala needs its backup vendor Veeam Software to add vSphere Server 6.5 to its offering.
HA has become more important as organizations' reliance on their computers has grown. VMware improved its HA features in the latest version of vCenter Server, reducing failover time and enhancing granularity. This step moves businesses closer to, but still a bit short of, 100% uptime.
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